Variable displacement pump



VARIABLE DISPLAQEMENT PUMP Patented E4, C1946 VARIABLE DISPLACEMEN T PUMP Joseph F. J oy, Claremont, N. H.

Application January 14,-1942, serial No. 426,729

7 Claims.-

' (Granted under the act of March s. 1883, as amended April 30, 1928; 370 0. G. 757) The invention described herein may be manu-v factured and'used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to a variable displacement hydraulic pump.

In the employment of hydraulic power driven devices it is desirable that the displacement of the driving pump be capable of variation in response to load pressures. Such variable displacement furnishes a convenient means of limiting maximum pressures and of maintaining a sub` stantially constant pressure through relatively large variations in output. Further, in the case Where such a pump is used as one link of a power transmission chain from a prime mover, through a pump, to driven hydraulic m'otors, variable dis- `placement provides a practically infinite number of gear ratios automatically variable in response to the loads applied at the hydraulic motors.

It is therefore an object of this invention to produce a self-contained hydraulic pump having an automatically controlled variable displacement and capable of efficient operation through a wide range of capacity. A

' The'specifc nature of the invention as wellas other objects and advantages thereof will clearly appear from the description. of a preferred embodiment as shown in the accompanying drawings in which:

Figure 1 is a longitudinal sectional view of an embodiment of my invention.

Figure 2 is a cross sectional view of the pump shown in Figure 1 taken on the line 2-2 of that figure.

Figure 3 is a similar view taken on the liner 3-3 of Figure l.

Figure 4 is a fragmentary sectional view taken on the line 4-4 of Figure 1.

Referring to the drawings by characters of reference the pump shown therein comprises a cylindrical main casing I in which have been formed a plurality of spaced cylinders 2 parallel with the axis of the casing and extending longitudinally therethrough. Pistons 3V adapted to reciprocate in the cylinders 2 are housed therein. Inlet valve ports 4 have been formed in the casing adjacent each of the cylinders and provided with 'valves 5 adapted to permit fluid to flow from the inside of the casing to the cylinders but to prevent reverse flow. A plate 6 engages the end of the main casing and has formed in it recesses 'I to guide the valves 5 and outlet ports 8 in alignment with each of .the cylinders 2. An end housing 9 is secured to the main casing I by suitable bolts I0', engaging the plate 6 and the main casing I. An annular channel l I is formed in the end housing in opposition to the ends of the cylinders and valve guide holes I2 each having a milled slot I3 intersecting the hole are provided to serve as guide means for each of the valves I4 seated on i the outlet ports 8. A pressure conduit I5 in comof the bushing between the annular channel II t and an annular groove 20 in the inner surface of the bushing.- Holes YI communicate between the groove 20 andthe chamber I8 in the shaft I1 so that the pressure in the annular channel is' thus duplicated .in the hollow shaft. A shaft extension 22 closes the end of the hollow shaft and extends outside the end housing through an antifriction bearing 23 and an oil retainer 24. The shaft extension is adapted to be coupled to any suitable source of driving power. Extending longitudinally through the bushing I6 are a plurality of holes 25 serving to connect the space between the oil retainer and the bushing with the interior of the main casing. This will serve to prevent any excess pressure from acting on the oil retainer in the event of leakage from the high pressure grQove 20 and hence along the shaft surface.

A bell housing 25 is secured to the other end of the main casing I and serves as a container for fluid which is returned to it through the conduit 21 and as a support for the bearing 28 which engages the main shaft Il. As has been previously explained the shaft I'I is provided with a pressure chamber I8 in its interior. A transverse slot 29 is provided in the opposite end of the shaft and an axial passage 30 communicates between this slot and the chamber I8. Closely fitting but slidable in the passage 30 is a control bar 3l threadably engaging a cross bar 32 in the slot and provided at the end within the chamber I8 with a collar 33 and nut 34 confining a spring 35 which tends to draw the contrpl bar into the chamber. The uid pressure in the chamber will act on the area of the bar in opposition to the spring, tending to force the control bar out of the chamber on an increase in chamber pressure. A

Transverse pivts 36 are secured to the shaft .parallel with the transverse slot 29 and acollar ceives 'a pin 39 which retains a pair of links 40 connecting the eye with the ends of the cross bar 32 and secured thereto with a pin 38h in such a manner that the collar will be coamal with the shaft when the spring 3,5 is compressed to the limit of its resistance. It will be seen, therefore, that the collar will have its maximum inclination when the spring 35 is fully extended and no pressure is acting in opposition thereto and that the inclination of the collar with respect to the shaft will vary in an inverse ratio to the pressure until a limiting pressure is reached, at which the inclination will be zero.

A band 4l surrounds the collar 3l and thrust transmitting bearings 42 allow the collar to be rotated with respect to the band while thrust from the collar will be transmitted to the band. The band supports a plurality of ball headed members 43, one of these members 43 being opposed to each cylinder 2. Similar ball heads 44 have been formed on each of the pistons 3 and a link 45 comprising a pair of similarly shaped plates is clamped upon all but the bottom pair of the piston heads 44 and their corresponding ball members 43 in such a manner as to allow each link to oscillate on the balls while transmitting reciprocating motion from one ball to the other. A special link 46 is engaged upon the bottom piston head 44 and its corresponding ball member 43 in similar fashion to the links 45 engaging the other piston heads. The link 46 differs from thelinks 45 in that outer side faces 4l have been machined flat in planes parallel to the axis of the piston. To secure the band- 4l carrying the members 43 against any misalignment arising out of its tendency to rotate with the main shaft l1, a pair of special guide lugs 48, having opposed finished surfaces `47a between `which the side faces 41 of the link 46 are arranged to oscillate, may be provided on the inner wall of the end casing 26 as shown in Figs. l and '4. It will be obvious that as the inclined collar is rotated with the shaft the pistons will be reciprocated in the cylinders and that as the inclination of the collar is decreased the stroke of the pistons will be reduced. In this manner a pump has been produced in which the displacement varies automatically in inverse ratio to the outlet pressure.

primary stage. This impeller may take the form,

of an Archimedean screw 49 secured on the shaft and running in a close fit with the inner wall of the casing or some other form of impeller such as a gear or propeller type may be used.

summarizing the operation of the pump it will be seen that under no load the stroke regulating spring will be fully extended under which condition rotation of the shaft will causeeach piston in turn to be drawn through its full stroke cycle of intakeand exhaust, displacing a maximum volume of fluid in a given time. As the load pressure is built up the pressure will be communicated through the passages provided into the chamber in the drive shaft, acting`l on the control bar to compress the regulating spring and through the linkage to reduce the inclination of the collar and correspondingly reduce the displacement of the pistons. The tension on the spring will be so adjusted that at the desired maximum pressure the inclination of the collar will have been reduced to zero.

It has also been contemplated that a pinion and rack arrangement or other equivalent means might be substituted for the linkage shown for controlling the inclination of the collar.

I claim:

1. Displacement regulating means for a pump having a shaft and a plurality of reciprocable pistons parallel therewith,said means comprising -a pressure chamber in said shaft, a passage in said shaft communicating with said chamber, a bar in said chamber and extending through said passage, spring means impelling said bar further into said chamber, a, transverse pivot through said shaft, a collar surrounding said shaft and swingable about the axis of said pivot for inclination with respect to said shaft, thrust transmitting .means oetweemsad collar and said pistons, and means interconnecting said bar and said collar whereby the inclination of said collar with respect to said shaft may be decreased as pressure in said chamber tends to expel said bar.

2. Displacement regulating means as described in claim 1, said interconnecting means comprising a link engaged between the end of said bar and said collar.

3. A pump comprising a shaft, an inclined co1- lar surrounding said shaft, a cylinder parallel with said shaft, a piston in said cylinder, a ball end on said piston, a thrust transmitting bea-ring on said collar, a band engaging said bearing to receive thrust from said collar, a ball member on said band, and a link having means gripping the ball end on said piston and the ball member on said band.

4. A pump, comprising: housing means. at least a part of which'forms a fluid reservoir; cylinder means, formed in said housing means, the fluid intake of said cylinder means opening directly into said reservoir; piston means, operable in said cylinder means; shaft means, having at least a portion extending through said reservoir; motion transmitting means disposed within said reservoir, and having connection with said shaft means and said piston means, constructed and arranged to transmit motion of said piston means to said shaft means; and means, within said reservoir and actuated by motion of said shaft, constructed and arranged to urge fluid within said reservoir in a direction toward the place where said cylinder means open into said reservoir.

5. A pump, comprising: shaft means, adapted to be rotated; a fluid reservoir enclosing at least part of said shaft means, and having at least a part of its interior surface coaxial with said shaft; a plurality of cylinders positioned substantially parallel with the axis of said shaft, and arranged in spaced-apart relation on a circle coxial with said shaft, each cylinder having its intake opening into a transverse defining wall of the coaxial part of said reservoir; and impeller means rotatable With said shaft within the coaxial part of said reservoir, constructed and arranged to urge fluid longitudinally of said coaxial part and in a direction toward said transverse deiiningwall.

6. A fluid pump, comprising: a rotatable shaft, having a pressure chamber in fluid communication with outlet fluid pressure of said pump; a plurality of fixed cylinders substantially parallel to and surrounding said shaft; a piston reciprocable within each of said cylinders; wobble means, including a part rotatable with said shaft and a part having connection with each of said pistons, constructed and arranged ior movement from a plane normal to the axis of said shaft to a plane at an angle to said rst mentioned plane; piston means, reciprocable within said shaft pressure chamber and having mechanical connection with said wobble means, so that reciprocation of said piston means directly eii'ects change in inclination of said wobble means; resilient means, pro-- vidng a fixed urging force, and urging said piscable within each of said cylinders; wobble means, including a part rotatable with said shaft and a part having connection with each of said pistons,

constructed and arranged for movement from a ton means in one direction to yieldably maintain said wobble means in one position; said piston means being movable in the opposite direction only by fluid pressure developed by said pump.

7. A fluid pump, comprising: a rotatable shaft, having a pressure chamber in duid communication with outlet nuid pressure of said pump; a plurality of xed cylinders substantially parallel to and surrounding said shaft; a piston reciproplane normal to the axis of said shaft wherein the pump has zero displacement, through successively increasing angular positions to a plane at a predetermined maximum angle to said rst mentioned plane wherein the pump' has maximum displacement; piston means, reciprocable within said shaft pressure chamber and having'connection with said wobble means; resilient means, providing a. xed urging force, urging said piston means in one direction to yieldably maintain said wobble means yin its maximum angle of inclination to` provide for maximum displacement; said piston means being movable in its other direction only by pressure developed by said pump so that said wobble means is moved toward said normal plane as the pressure increases.

JOSEPH F. JOY. 

